Originally Posted by Unsane
It's a new bike. I think that it's not shifting fully into or out of the lower gears. When I am pedaling it is very jerky like there are teeth missing on one of the sprockets and makes an awful sound but I checked them out and all seems fine. I know its going to make noise, but this seems unsafe because my feet coming flying off the pedals when it does this.
Click the link below to learn how to repair your bike. It lists every bike repair known to man kind. With pictures!!! BTW, the other guy asked you if it was the front or rear derailleur. that is sort of important to know before we can help you. Go to the link and study. Then come back and ask questions.
http://www.parktool.com/repair_help/FAQindex.shtml